Tool balancers are in widespread use in manufacturing, and they have particular acceptance where the tool being used transmits torque to the hand of the assembly worker. If torque is transmitted from the tool to the hand, wrist and arm of the worker, it has been found to produce muscle stress, which, in turn, contributes to the risk of repetitive motion injury (RMI) to the worker. Thus, some tool balancers have been designed to reduce the transmission of torque from the tool to the hand and arm of the worker.
In addition, where the assembly may continue over a number of hours, the worker's holding of the tool may induce additional muscle stress due to the weight of the tool. Therefore, there has been an attempt to design tool holders to balance the weight of the tool in addition to resisting or neutralizing torque produced by use of the tool. In order to accommodate the tool balancers to tools of different weights, it is deemed desirable to have the counter-balancing mechanism be adjustable. There are a number of techniques available for adjusting the counter-balancing force on the arm of a tool holder, but they have either required the use of a tool to produce the adjustment, or they have required the use of an adjusting screw to secure a bracket to an upright or standard on which the tool support arm is mounted, such as is shown in U.S. Pat. No. 4,969,626. The prior methods of providing an adjustment are either inconvenient or time consuming, in the case where they require a tool to effect the adjustment, or they are not readily accommodated to a tool balancer having an articulated support arm.